The stage is the late 19th century. The Kingdom of Albion was divided due to the Republican Revolution. The capital city of London is divided by a huge wall. The east side is ruled by the Kingdom and the west side is ruled by the Republic. It has become the front line of the Shadow War where spies from various countries are active. Ten years after the revolution, five girls disguised as high school girls appeared at Mayfair Queen's School, a prestigious school in the kingdom, and acted as spies for the Republic. After preventing the Queen's assassination attempt and recuperating in Casablanca, they received new instructions from Control. Taking this mission as an opportunity, the five girls - Team Bai Ge - began to be involved in the huge whirlpool that shook the country.
